Download Crystal Oscillator Circuit and Working

Crystal Oscillator Circuit
and Its Working
Crystal Oscillator Circuit and Working
Introduction:
 A crystal oscillator is an electronic oscillator circuit which is used for the
mechanical resonance of a vibrating crystal of piezoelectric material. It
will create an electrical signal with a given frequency. This frequency is
commonly used to keep track of time. Crystal oscillators must be
designed to provide a load capacitance.
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Crystal Oscillator Circuit and Working
Different Types of Oscillator
 Linear oscillators – Hartley oscillator, Phase-shift oscillator,
Armstrong oscillator, Clapp oscillator, Colpitts oscillator.
 Relaxation oscillators – Royer oscillator, Ring oscillator,
Multivibrator Oscillator and Voltage Controlled Oscillator
(VCO).
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Crystal Oscillator Circuit and Working
What is a Quartz Crystal?
 A quartz crystal exhibits a very important property known as the
piezoelectric effect.
 When a mechanical pressure is applied across the faces of the crystal.
 A voltage which is proportional to mechanical pressure appears across
the crystal.
 That voltage causes distortion in the crystal.
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Crystal Oscillator Circuit and Working
What is a Quartz Crystal?
 Distorted amount will be proportional to the applied voltage.
 An alternate voltage applied to a crystal it causes to vibrate at its
natural frequency.
 Quartz crystal in an electronic oscillator that consists of resistor,
inductor, and capacitors.
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Crystal Oscillator Circuit and Working
Quartz Crystal Circuit
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Crystal Oscillator Circuit and Working
Crystal Oscillator Circuit Diagram
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Crystal Oscillator Circuit and Working
Crystal Oscillator Circuit Diagram
 Bipolar transistors or FETs are used in construction of Crystal oscillator
circuits.
 Because operational amplifiers can be used in different low frequency
oscillator circuit.
 It is below 100KHz but operational amplifiers do not have the
bandwidth to operate.
 It will be a problem at the higher frequencies that are matched to
crystals which are above 1MHz.
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Crystal Oscillator Circuit and Working
Crystal Oscillator Circuit Diagram
 To overcome this problem Colpitts crystal oscillator is designed.
 It will work at higher Frequencies.
 In this Oscillator, the LC tank circuit that provides the feedback oscillations
has been replaced by a quartz crystal.
 Crystal Oscillators, that works with 16MHz frequency.
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Crystal Oscillator Circuit and Working
Crystal Oscillator Working
 Crystal oscillator circuit usually works on the principle of the inverse
piezoelectric effect.
 The applied electric field will produce a mechanical deformation across
some materials.
 It utilizes the vibrating crystal’s mechanical resonance.
 It is made with a piezoelectric material for generating an electrical signal
of a particular frequency.
 Quartz crystal oscillators are highly stable.
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Crystal Oscillator Circuit and Working
Crystal Oscillator Working
 They consists of good quality factor(Q), they are small in size, and are
economically related.
 Quartz crystal oscillator circuits are more superior compared to other
resonators like LC circuits, turning forks.
 Generally in Microprocessors and Micro controllers we are using an
8MHz crystal oscillator.
 The equivalent electrical circuit is also describes the crystal action of the
crystal.
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Crystal Oscillator Circuit and Working
Crystal Oscillator Working
 The basic components used in the circuit are....
 Inductance L represents crystal mass
 Capacitance C2 represents compliance.
 C1 is used to represent the capacitance that is formed because of crystal’s
mechanical moulding.
 Resistance R represents the crystal’s internal structure friction.
 The quartz crystal oscillator circuit diagram consists of two resonances such
as series and parallel resonance.
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Crystal Oscillator Circuit and Working
Crystal Oscillator Working
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Crystal Oscillator Circuit and Working
Crystal Oscillator Working
 The series resonance occurs when the reactance produced by
capacitance C1is equal and opposite to the reactance produced by
inductance L.
 The fr and fp represents series and parallel resonant frequencies
respectively.
 The values of ‘fr’ and ‘fp’ can be determined by using the following
equations.
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Crystal Oscillator Circuit and Working
Uses of Crystal Oscillator
 In the design of microprocessors and microcontrollers, crystal
oscillators are used for the sake of providing the clock signals.
 In 8051 microcontroller an external crystal oscillator circuit will work
with 12MHz that is essential.
 This particular crystal oscillator which is having cycle rate at 1MHz to
3.33MHz is used to generate clock pulses.
 It is required for the synchronization of all the internal operations.
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Crystal Oscillator Circuit and Working
Application of Crystal Oscillator
 There are various applications for crystal oscillator in various fields and
some of crystal oscillator applications are given below.
 Colpitts Crystal Oscillator Application
 Applications of Armstrong Crystal Oscillator
 Industrial Applications of Crystal Oscillator
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Crystal Oscillator Circuit and Working
Colpitts Crystal Oscillator Application
 Colpitts Oscillator is used to generate a sinusoidal output signal at
very high frequencies.
 Colpitts oscillator can be used as the different types of sensors such
as temperature sensor.
 Using of SAW device in Colpitts circuit it senses directly from its
surface.
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Crystal Oscillator Circuit and Working
Colpitts Crystal Oscillator Application
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Crystal Oscillator Circuit and Working
Colpitts Crystal Oscillator Application
 The applications of the Colpitts oscillators mainly involve where the wide
range of frequencies is used.
 It is used in undamped and continuous oscillation condition.
 Using some devices in Colpitts circuit, we can achieve greater
temperature stability and high frequency.
 Colpitts used for the development of mobile communications and radio
communications.
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Crystal Oscillator Circuit and Working
Applications of Armstrong Crystal Oscillator
 These are widely used in the regenerative radio receivers.
 In that input, radio frequency signal from the antenna is coupled
magnetically into the tank circuit through an additional winding.
 Feedback is reduced to gain control in the feedback loop.
 It produces a narrow-band radio-frequency filter and amplifier.
 In this Crystal oscillator LC resonant circuit is replaced with
feedback loops.
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Crystal Oscillator Circuit and Working
Applications of Armstrong Crystal Oscillator
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Crystal Oscillator Circuit and Working
Applications of Armstrong Crystal Oscillator
 In Military and Aerospace
 Used for the efficient communication system.
 Crystal Oscillators are used in military and aerospace.
 The communication system is to establish and for the navigation
purpose and electronic warfare in the guidance systems
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Crystal Oscillator Circuit and Working
Applications of Armstrong Crystal Oscillator
 In Research and Measurement
 The crystal oscillators are used in research and measurement for the
celestial navigation and the space tracking purpose
 The crystal oscillators are used in medical devices and in the measuring
instruments.
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Crystal Oscillator Circuit and Working
Industrial Applications of Crystal Oscillator
 There are many industrial applications of the crystal oscillator.
• They are widely used in computers.
• Used in Instrumentation.
• Used in digital systems.
• Used in phase locked loop systems.
• Used in Modems and marine
• Used in telecommunications.
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Crystal Oscillator Circuit and Working
Industrial Applications of Crystal Oscillator
 Used in sensors.
 Used in disk drives.
 Used in engine controlling.
 Used in clock and to trip computer.
 Used in Stereo.
 Used in GPS systems.
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Crystal Oscillator Circuit and Working
Industrial Applications of Crystal Oscillator
 Crystal oscillators are used in many consumer goods.
 Used In cable television systems.
 Used In video cameras.
 Used In personal computers.
 Used In toys and video games.
 Used In cellular phones.
 Used In radio systems.
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Crystal Oscillator Circuit and Working
Conclusion
 This is all about what is a Crystal Oscillator, its working and Applications.
Quartz crystal is mainly used in radio-frequency (RF) oscillators. We have
seen the circuit diagram working of crystal oscillator. Quartz crystal is
the most common type of piezoelectric resonator, in oscillator circuits
we are using them so it became known as crystal oscillators.
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